\documentclass{standalone}
\usepackage{tikz}

\usepackage{../../style/csmacros}

\usepackage{color}
\definecolor{blueedf}{RGB}{0,91,187}
\definecolor{orangededf}{RGB}{254,88,21}

\newcommand{\orange}[1]{
\textcolor{orangededf}{#1}}
\newcommand{\blue}[1]{
\textcolor{blueedf}{#1}}

\begin{document}
\begin{tikzpicture}[scale=0.3, transform shape]
      % Fluid Region
      %   Cell i
      \draw (3,4)  -- (4,6) -- (7,4) -- (9,0) -- (6,-3) -- (3,-1) [white,fill=blue!10];
      % Mesh
      % Cell i
      \draw[orange] (3,4)  -- (4,6) -- (7,4) -- (9,0) -- (6,-3) -- (3,-1) -- cycle ;
      \draw[orange] (5,3.5) node[above]{\Huge $\orange{\Omega_{\celli}}$};
      %contour cells
      \draw[blueedf,line width=1.] (3,4) -- (3,-1);
      %   Line IJ
      \draw (5.5,0.5) node[black,below]{\Huge $\centi$} ;
      \node[circle,draw=black, fill=black, inner sep=0pt,minimum size=7pt, line width=0.5] (b) at (5.5,0.8) {};
      \draw [-,black](3,1.5) -- (5.5,0.8);
      %   Line I'J'
      \draw [-,dashed,black](3,1.5) -- (5.5,1.5) ;
      \draw [-,dashed,black](5.5,0.8) -- (5.5,1.5) ;
      \draw (5.5,1.5) node[black,above]{\Huge $\centip$} ;
      % Angles
      \draw (3,1.5) -- (3.2,1.5) -- (3.2,1.3) -- (3,1.3) -- cycle;
      \draw (5.5,1.5) -- (5.3,1.5) -- (5.3,1.3) -- (5.5,1.3) -- cycle;
      %   Points at the face
      \draw [-stealth,blueedf,line width=1.](3,1.5) -- (4.5,1.5);
      \draw (3.75,1.5) node[blueedf,above]{\Huge $\vect{S}_{\fib}$};
      \draw (3,1.5) node[black,left]{\Huge $\centfb$};
      \node[circle,draw=black, fill=black, inner sep=0pt,minimum size=7pt, line width=0.5] (b) at (3,1.5) {};

\end{tikzpicture}
\end{document}
